| Sreen of inutagenic strains of A. niger N25 and sequence analysis of its phyA expression gene LuoYan , WangHongNing et a]. (College of Animal Technology & Science, Sichuan Agricultural University, Ya抋n, Sichuan, 625014) Abstract In this research, two antibiotic梤esistant mutagenic strains (N25? and N25?) by UV (ultraviolet radiation) for improved phytase production were screened. The producing enzyme condition of strain N25? was studied.The phyA expression gene from strain N25? was amplified cloned and sequenced. The following are n~in research results: 1 The phytase activity of strain N25? and N25? were 2. 5 and 3. 0 times than the natural strain N25, respectively. The method of the single梥pore 梥uspendedæ¢iquid preparation and count,the optimum mutagenic time determination and the initial screen of mutagenic strain was improved. 2-. When strain N25? was cultivated in different PH medium, phytase activity reached a peak value(1551. l7nnx,l/ml.min) in P113.0. When strain N25? was cultivated for different time, phytase activity reached the highest level between 72?6h. The optimum PH of strain N25? phytase was 4. 6, and there were another two phytase activity peak values in P112. 3 and P117. 4. The optimum temperature of strain N25? phytase was 370C, and there was anthoer phytase activity peak values in 65扖.The strain N25? phytase had a good P1-I stability and a good heat stability. The strain N25? also had a good genetic stability, and almost eliminated the revivatory sensitivity to the visible light. 3~, The phyA expression gene of strain N25? was amplified by the polymerase chain reaction(PCR) and the amplified fragment was cloned and sequenced. Comparison of this sequence with the phyA expression gene of 38 natural strain N25 showed there was two different bases between the two sequences,while had the same amino acid.Comparied research of phyA expression gene between mutagenic strain N25? and natural strain N25 is not studied at home and abroad. |
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